This is an application to establish a Center for Neuroscience Research (CNR) on NEURONAL POPULATIONS AND BEHAVIOR. The main thrust of the proposed center would be toward understanding hoe interacting populations of neurons in the cerebral cortex and cerebellum are able to control sensory-motor and perceptual-motor behaviors. We seek understanding at three levels: (1) At the level of representations--we will study how perceptual-motor processes are represented by cellular activity in the cerebral cortex and cerebellum. (2) At the level of operational mechanisms--we will investigate cellular and network mechanisms that the brain uses to regulate patterns of activity in these populations and explore how the spatiotemporal patterns are then harnessed to control the behavior of the organism. (3) At the level of adaptive mechanisms--we will study the mechanisms that the brain uses to update existing representations in interacting neuronal populations and the mechanisms used to learn new representations for dealing with novel perceptual-motor experiences. There will be five project areas: A. Representations of perceptual-motor processes in populations of cerebral cortical neurons will be studied by recording single unit activity in association with cognitive and memory- related behaviors. B. Adaptive network models of sensory-motor and perceptual-motor processes will be developed and used to explore how neuron properties and population activity might cooperate in the control of behavior. C. Operational mechanisms for regulating communication between populations of neurons in motor cortex and cerebellum will be studied with correlational methods and multiple single unit recordings. D. In itro neural networks isolated from the turtle or grown in tissue culture will be used to study celllular and network mechanisms for controlling spatiotemporal patterns in neuronal populations. E. Adaptive mechanisms whereby representations in neuronal populations can be adjusted to novel perceptual-motor experiences will be studied using the cerebellar flocculus as a model system. The proposed CNR addresses the critical question of how populations of neurons are used by the nervous system to translate between mentation and action. This is an important question, the answer to which would greatly enhance our understanding of mental health and mental illmess.